The total annual electrical energy production in the United States is about 4000TWh, while the useful heat produced by cogeneration is about 1500TBtu annually. Use these figures to confirm the statement that only about 5% of waste heat from electric power generation gets used. Assume 33% average power generation efficiency. Solution One measure of the efficiency of a generator or power plant that converts a fuel into heat and into electricity is the heat rate . The heat rate is the amount of energy used by an electrical generator or power plant to generate one kilowatthour (kWh) of electricity. The U.S. Energy Information Administration (EIA) expresses heat rates in British thermal units (Btu) per net kWh generated. Net generation is the amount of electricity a power plant (or generator) supplies to the power transmission line connected to the power plant. Net generation accounts for all the electricity that the plant itself consumes to operate the generator(s) and other equipment, such as fuel feeding systems, boiler water pumps, cooling equipment, and pollution control devices. To express the efficiency of a generator or power plant as a percentage, divide the equivalent Btu content of a kWh of electricity by the heat rate.For example, if the heat rate is 10,500 Btu, the efficiency is 33% .